package org.csmzclass2333;

public class example02 {
        public static void main(String[] args) {
            int n = 20;
            long sum = 0;
            long first = 1;
            long second = 1;
            long next;

            sum += first + second;

            for (int i = 3; i <= n; i++) {
                next = first + second;
                sum += next;
                first = second;
                second = next;
            }

            System.out.println("斐波那契数列前20项之和为: " + sum);
        }
    }
